Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$94.33	10.517%	$104.2507	$104.25	$104.25	$104.30
Purchase #2	$209.42	8.533%	$227.2898	$227.29	$227.30	$227.30
Purchase #3	$30.34	7.389%	$32.5818	$32.58	$32.60	$32.60
Purchase #4	$25.75	12.393%	$28.9412	$28.94	$28.95	$28.90
Purchase #5	$19.82	3.279%	$20.4699	$20.47	$20.45	$20.50
Purchase #6	$166.55	3.517%	$172.4076	$172.41	$172.40	$172.40
Purchase #7	$129.92	7.216%	$139.295	$139.30	$139.30	$139.30
7 purchase totals =	$676.13		$725.2360	$725.24	$725.25	$725.30